A combustion engine comprises an engine block delimiting combustion chambers which are connected to a fresh gas inlet line and to a burnt gas exhaust line. Mounted in the inlet line is a flow regulating butterfly valve the position of which is determined by the extent to which the throttle pedal of the vehicle is depressed in order to control the rotational speed of the engine. A turbine for driving a compressor mounted in the inlet line is generally mounted in the exhaust line.
It is known practice in internal combustion diesel engines to fit between the inlet line and the exhaust line an exhaust gas recirculation circuit that recirculates exhaust gases to the inlet line. Such a recirculation circuit generally comprises a valve that regulates the flow passing through the recirculation circuit. The recirculation circuit is generally connected to the exhaust line upstream of the turbine and to the inlet line downstream of the compressor (this is the recirculation circuit type known as a high-pressure circuit).
The plan is, in the future, to equip internal combustion gasoline engines with a recirculation circuit which would be connected to the exhaust line downstream of the turbine and, more specifically, downstream of the catalytic converter, and to the inlet line upstream of the compressor (the recirculation circuit would then be of the low-pressure type) in order to reduce the exhaust temperature and increase the resistance to pinging of these engines. That however assumes that the flow rate of gases through the recirculation circuit can be regulated precisely and reliably over the entire engine operating range in order to limit the pollutant emissions of this engine, stabilize combustion and prevent the onset of pinging. Regulation is generally performed using a measurement of the difference in pressure between the pressure upstream and the pressure downstream of the recirculation circuit flow regulating valve. However, at light load, this pressure difference is small and dictates the use of pressure sensors of an accuracy that makes them expensive.